Several arrangements related to the problems of such systems are known. For example in U.S. Pat. No. 3,916,123 the events taking place at a large number of independent input points are recorded. The drawback of this approach is that only independent events can be assessed and the system is not suitable for the supervision of input points, where the information is carried by the interrelation and, sequence of the events and not by the number and length of time of the events. A further disadvantage is that only those circuits or common units can be supervised, where the operative efficiency of the observed circuit or unit is characterized by a single input, since the simultaneous condition of two measuring points cannot be co-ordinated.
U.S. Pat. No. 4,117,278 provides an apparatus suitable for measuring the quality of the service, with the aid of which the quality of the service can be checked on different objects in a way significant to the subscribers. Here, however, the parameters characteristic to the quality of the service are not determined simultaneously with traffic and efficiency measurements, thus short of analyzing the causes of faults, intervention in the system is not possible.
Swiss Pat. No. 614170 provides in case of sub-exchanges for the collection of data related to the beginning and end of line seizures and/or tariff pulses in connection with each call. Since the apparatus is connected only to the lines of the telephone extensions, it does not give sufficient information on the operation of the total exchange for automatic intervention.
U.S. Pat. No. 3,796,837 provides traffic control of networks. A disadvantage of this system is that only the limitation of the calls among the control possibilities of the traffic is realized in case of overload, which is due to the fact that all of the traffic technical parameters of the telephone exchanges are not measured to the point that suitable methods of the traffic control could be selected.
Furthermore the AOM 101 type system of the Swedish Ericsson firm is also known, which supervises electronic telephone exchanges, but can be connected to electro-mechanical exchanges as well. However, with electro-mechanical exchanges the traffic of calls and efficiency of the telephone circuits can be measured only on those circuits which are provided with contacts for this purpose. There are line plug connectors in such installations which do not contain this additional information.